A bit after sunrise on June 6, 2025, NASA’s 2001 Mars Odyssey orbiter saw one of Mars’ biggest volcanoes, Arsia Mons, as it broke through the clouds. The volcano is the cloudiest of the Tharsis volcanoes, a trio that is tightly aligned on Mars’ surface.
What is it?
Standing at over 12 miles (20 kilometers) with a diameter of 270 miles (450km), Arsia Mons is nearly twice as high as Mauna Loa, Earth’s largest volcano, which sits at 6 miles (9 kilometers) from the seafloor.
Due to its height, Arsia Mons is often covered by clouds that form when expanded air that was blown up the sides of the volcano rapidly cools. These clouds can be especially thick during aphelion, a period where Mars is farthest from the sun in its orbit. Clouds that form during this time at the planet’s equator are known as the aphelion cloud belt, according to NASA.
Where is it?
Arsia Mons is the southernmost volcano in a trio called the Tharsis Montes, or the Tharsis mountains, which are located in Mars’ western hemisphere near its equator. The alignment of the Tharsis volcanoes suggests that a large fracture may have been responsible for the eruptions that formed all three volcanoes, according to NASA’s Jet Propulsion Laboratory (JPL).
To the northwest of the group stands Olympus Mons, the biggest volcano in the solar system, at 16 miles (25 kilometers) high.
Why is it amazing?
Because of its cloud cover, Arsia Mons has been hard to photograph. This new image from NASA’s 2001 Mars Odyssey orbiter gives a first-of-its kind view at the peak of the volcano. The picture is also the first time any of the three Tharsis volcanoes has been captured on the horizon, offering a similar perspective as what astronauts see from the International Space Station when they view Earth, according to NASA.
Unlike other regions of the planet, the clouds that surround this volcano are made of water ice, which remains in Mars’ atmosphere most of the year. In fact, the Martian atmosphere contains more water vapor than the upper layers of Earth’s atmosphere, according to JPL. Other areas of Mars contain dust storms made of carbon dioxide clouds. Studying these cloud formations helps experts to better understand how storms form and occur on the Red Planet.
Want to learn more?
You can read more about Martian volcanoes and cloud storms as scientists dive further into the features of our planetary neighbor.